Good kite photos on another thread. Re this thread, point taken. I'm fairly consistent in minimal wording though and there are others better informed and more analytical than me! I'm wrong disappointingly often it seems, but to answer your question directly (and acknowledging other methods are quite possibly better), these 'identify this' posts come down to 3 things for me. I failed miserably with a recent sparrowhawk photo so don't even stick to my 3 things, but they're, 1) read what the poster wrote 2) what does the bird look like? 3) is that likely? Obviously, in a chiffchaff v willow warbler type post, 3) isn't really relevant. The person with the best opportunity is the poster as he saw the bird. He believes it's a willow warbler. Looking at the photos, they're not exactly telling us that he's wrong. The photos could be of a rarity. They aren't 100% conclusive imo. But, weighing things up, do the photos prove against the following?:- long primary projection, dark eye stripe, long whitish supercilium, legs rather pale, pale centre ear coverts with dark lower border, yellowish basal half of lower mandible rather sharply demarcated from dark tip etc. I don't believe the photos do prove against those things. Do the photos prove against some of the following?:- dark legs in palest case dark grey brown, prim projection c60%, fine usually dark bill usually ill defined pale base, less stronger bill than WW with pale cutting edge etc. In my opinion, there's nothing to suggest john l is wrong, and from what can be seen, on the face of it there's more to suggest the alternative put forward is wrong.

We can also debate the definition of, "very unreliable". Personally, it's another year going by and I've still yet to see a pale legged chiffchaff singing in this country, ever. I know there's been discussion before, and ww are sometimes seen with darker legs (WWT Slimbridge even highlighted one being there, which implies to me they too treat it as infrequent even in the 'more common' leg reversal), but away from the forum I've yet to read or hear anything support the theory that there are numerous chiffchaffs without dark legs in the UK each May. Not wishing to debate or cause issues. Just answering your question, TJ, as per request. If anyone can provide any evidence to help improve my understanding, I'd appreciate it.

I should have written that in my opinion john l is probably right that it's likely to be a ww.

Cheers.

Rob

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If it's only a very small minority of Chiffchaffs with pale legs, the feature is still pretty reliable! Still worth using it, but obviously use something else as well. But then, with the Chiff/Willow issue, all features except song seem to be 'unreliable', so just use as many as you can when making an ID. I'd go for this one being WW, mostly as it has relatively dark legs (it looks like to me...) with yellow feet, as well as overall colour, eyestripe etc.

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I mean percentage probability, not volume of people saying one thing or another. Obviously, if someone's in a minority of one, clearly that person needs to stand back and reflect. May not be wrong, but worth doing anyway. But, I mean if it's 1% chance of being A and 99% chance of being B, it's not ideal to say it can't be positively i.d'd imo.

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If it's only a very small minority of Chiffchaffs with pale legs, the feature is still pretty reliable! Still worth using it, but obviously use something else as well. But then, with the Chiff/Willow issue, all features except song seem to be 'unreliable', so just use as many as you can when making an ID. I'd go for this one being WW, mostly as it has relatively dark legs (it looks like to me...) with yellow feet, as well as overall colour, eyestripe etc.

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p.s. what's probably most important, I suspect, is John L wants an i.d. that's as close to accurate as possible. I think there's consensus that it won't be 100% guaranteed, but I suspect he's only after a very good probability. I think a number of chiffchaff v willow warbler i.d photos, esp the single ones, are percentage i.d's anyway.

I think that the real problem here is that it really isn't always possible to give an ID - which is something that has to be realised with all wildlife. Sometimes you just have to be prepared to let a bird go as unidentified.

It is often possible to say that based on visible features there is, for instance, a 90%, 75%, or 60% chance that a warbler like this one is a Willow Warbler rather than a Chiffchaff, but that is really only a different way of saying that the bird can't be identified.

In this case the clean underparts, the extent of the pale bill base, and the pale(ish) brown legs are all features that tend to be seen more on Willow Warbler, but the solidly dark cheeks, obvious white crescent below the eye, and perhaps the relatively weak supercilium are more pro- Chiffchaff. In my opinion what can be seen of the wingtips is of no use for the ID at all; the shape of the wingtips, as in whether they look pointed or blunt, is not important, what matters is how long the projecting primaries are in comparison to the length of the tertials (which does mean that the wings of Willow Warbler can seem longer - but wing length is very difficult to judge, especially from the angle shown, and the primary projection cannot be seen in these photos).

Personally I would say that the identification of this warbler is probably tipped in favour of Willow based on what can be seen, but it is a close call and this identification is probably no more than 60% certain.

For comparison:

Chiffchaffs with brown legs (similar in colour to the bird in this thread) -